Both chemotherapy and radioimmunotherapy induce dose-limiting myelosuppression. In fact, chemotherapy-induced myelosuppression is the most common dose-limiting, and potentially fatal, complication of cancer treatment. Maxwell et al., Semin. Oncol. Nurs. 8:113-123 (1992); Blijham, Anticancer Drugs 4:527-533 (1993). Drug-induced hematopoietic toxicity is a common reason for curtailing high dose chemotherapy in cancer patients (Boesen et al., Biotherapy 6:291-302 (1993)), and higher dose chemotherapy is only possible in conjunction with bone marrow transplantation (BMT), autologous stem cell infusion, and treatment with hematopoietic growth factors.
During the recovery period after anticancer myelosuppressive therapy, hematopoietic progenitor cells become mitotically active in order to replenish the marrow compartment and remain hyperproliferative even after normalization of peripheral white blood cells (pWBCs) and platelets (PLTs). At this stage, the progenitors are more radio- and chemo-sensitive. Dosing patients with additional cytotoxic therapy during this phase will likely result in more severe toxicity.
As a general model of myelosuppressive therapy, acute damage and recovery of hematopoietic stem and precursor cells following whole-body irradiation also has been studied extensively. Testa et al., Anticancer Res. 5:101-110 (1985); Sado et al., Int. J. Radiat Biol 53:177-187 (1988); Meijne et al., Exp. Hematol. 19:617-623 (1991). External beam irradiation results in long-term damage of hematopoietic stem cells, which manifests with the presence, but at sub-optimal levels, of mitotically active, hematopoietic progenitor cells (CFU-S) 3-6 months after treatment. Lorimore et al., Int. J. Radiat Biol 57:385-393 (1990); Lord et al., Int. J. Radat. Biol. 59:211-218 (1991). Persistent depletion of femoral and splenic CFU-S (colony forming unit-spleen), CFU-GM (colony forming unit-granulocytic-monocytic) and BFU-E (burst forming unit-erythroid) can occur, even though the peripheral blood contains normal cell numbers. Grande et al., Int. J. Radiat. Biol. 59:59-67 (1993). Severe reduction in the supportive stroma has also been reported. Tavassoli et al., Exp. Hematol. 10:435-443 (1992). Following radiation exposure, recovery proceeds by repair of sublethal cellular injury and compensatory cellular repopulation by the surviving fraction. Hall in Radiobiogy for the Radiobiologist (Harper and Row 1978); Jones et al., Radiation Res. 128:256-266 (1991).
Normal white blood cell (WBC;  greater than 4000/mm3) and platelet (PLT;  greater than 100,000/mm3) counts are the usual markers for patient tolerance to repetitive myelosuppressive treatment. However, preclinical and clinical evidence suggests that peripheral counts are not a reliable surrogate for predicting complete myelosuppressive recovery. Although WBC and PLT counts may appear normal, the primitive stem and progenitor cell compartments are not fully recovered from previous myelosuppressive therapy.
Further cytotoxic treatment while stem cells and progenitor cells are rapidly proliferating can result in more severe myelotoxicity or even death. One solution to this problem is to collect bone marrow (BM) aspirates and use a long-term culture system to quantitate high proliferative potential CFC (HPP-CFC) or long term culture initiating cells (LTC-IC). Eaves et al., Tiss. Culture Meth. 13:55-62 (1991); McNiece et al., Blood 75:609-612 (1989). While this method can provide the needed information, such assays take 3-6 weeks to perform, and thus are not clinically useful.
During hematopoiesis, pluripotent stem cells differentiate and proliferate in multiple lineages. The process proceeds under the permissive influence of xe2x80x9cearlyxe2x80x9d and xe2x80x9clatexe2x80x9d hematopoietic cytokines. Lowry et al., J. Cell Biochem. 58:410-415 (1995). xe2x80x9cEarlyxe2x80x9d stimulatory factors include SCF, FLT-3-L, IL-1, IL-3, IL-6, and IL-11. In addition to these positive regulators, hematopoiesis is also controlled by inhibitory cytokines. Negative regulation of myelopoiesis occurs through several inhibitory cytokines, most notably MIP-1xcex1 (Cooper et al., Expt. Hematol. 22:186-193 (1994); Dunlop et al., Blood 79:2221-2225 (1992)), TGFxcex23 (Jacobsen et al., Blood 78:2239-2247 (1991); Maze et al., J. Immunol. 149:1004-1009 (1992)) and TNFxcex1 (Mayani et al., Eur. J. Haematol. 49:225-233 (1992)).
Thus far a temporal change in these inhibitory peptides as a function of time after cytotoxic therapy has not been quantitated. It is known, however, that under stressful conditions, such as irradiation, chemotherapy, blood loss, infection or inflammation, both stimulatory and inhibitory growth factors play a major role in cellular adaptation processes. Cannistra et al., Semin. Hematol. 25:173-188 (1988). Under stress, the quiescent CFU-S component of the stem cell compartment is triggered into active cell cycling and returns to the predominantly G0G1 phase once normal bone marrow cellularity is restored. Becker et al., Blood 26:296-304 (1965).
The recent literature has highlighted several important areas where a noninvasive method to monitor myelorecovery could have considerable clinical benefit. For example, to improve the safety and cost effectiveness of high-dose regimens, hematopoietic cell support (cytokines) has been used to accelerate marrow recovery following myeloablative therapy. This approach results in an earlier recovery of peripheral blood counts, but the proliferative status of the marrow remains unknown and could be in a very active and sensitive state.
Another relevant example pertains to the use of allogeneic or autologous BMT, or more recently peripheral stem cell transplantation (SCT) following myelosuppressive or myeloablative therapy. Under those conditions, hematopoiesis is characterized by a prolonged and severe deficiency of marrow progenitors for several years, especially of the erythroid and megakaryocyte types, while the peripheral WBCs and PLTs have reached relatively normal values within a few weeks. Therefore, successful engraftment can not be measured by normalization of WBCs or PLTs, but requires another type of marker, perhaps one associated with normal marrow stromal function. Domensch et al., Blood 85:3320-3327 (1995). More information is needed to determine xe2x80x98truexe2x80x99 myelorecovery when either BMT or SCT is utilized. Talmadge et al., Bone Marrow Transplant. 19(2):161-172 (1997).
Yet, another area where a noninvasive measure of myelorecovery may be useful is for scheduling leukapheresis. Since patient-to-patient variability in time to marrow recovery is quite variable following G-CSF stem cell mobilization, it is difficult to predict the best time for this procedure. Identification of one or more markers of myelotoxic nadir and recovery could advance SCT technology. Shpall et al., Cancer Treat. Res. 77:143-157 (1997).
One investigator has shown that after allogeneic or autologous BMT, a rise in endogenous G-CSF levels precedes and correlates with myeloid engraftment. Cairo et al., Blood 79(7):1869-1873 (1992). Moreover, in patients suffering from acute bacterial infections, whose rate of myelopoiesis must adapt to the enhanced demand, G-CSF, but not GM-CSF, was elevated. Selig et al., Blood 79:1869-1873 (1995). Additional studies demonstrated that the stem cell subset responsible for reconstitution is responsive to GM-CSF, IL-3, IL-6, and SCF. Wagemaker et al., Stem Cells 13:165-171 (1995). Other reports have quantified one or more cytokines during a myelosuppressive episode. Sallerfors et al., Br. J. Hematol. 78:343-351 (1991); Baiocchi et al., Cancer Research 51:1 297-1303 (1996); Chen et al., Jap. J. Clin. Oncol. 26:18-23 (1996). Heretofore, however, no one looked at the recovery phase following myelosuppression, and there exists no correlation with the ability to redose without severe toxicity. A relatively new stromal cell-produced positive stimulatory cytokine, FLT-3-L (Brasel et al., Blood 88:2004-2012 (1996); Lisovsky et al., Blood 88(10):3987-97 (1996)), has not been studied at all to date regarding either constitutive or induced hematopoiesis.
Therefore, a need exists in the art for improved methods, and kits for implementing them, for predicting myelosuppressive recovery in conjunction with the foregoing deficient therapeutic techniques. Such methods could be used to help optimize treatment, informing the clinician of the appropriate timing of treatment, thus avoiding toxic effects, while maximizing efficacious ones. Provided such a method, the art would posses new, optimized methods of treatment.
It is therefore an object of the invention to provide kits and methods for evaluating the myelosuppressive state of a patient. According to this object, the invention provides a kit which contains at least one cytokine-specific detection reagent that is adapted to detect a threshold level of a cytokine, which correlates with the myelosuppressive state. In one embodiment, the cytokine specific reagent is specific for FLT3-L, TNF-xcex1 or TGF-xcex2, and the reagent may comprise an antibody or antibody fragment.
Also according to this object of the invention, a method of assessing the myelosuppressive state of a patient is provided. This method entails comparing the amount of at least one cytokine in a patient sample with a threshold level, thereby gauging the myelosuppressive state of the patient. In one embodiment, the cytokine specific reagent is specific for FLT3-L, TNF-xcex1 or TGF-xcex2, and the reagent may comprise an antibody or antibody fragment.
It is another object of the invention to provide an improved method of treating cancer. Further to this object, a method is provided where a patient is administered an effective amount of an anti-cancer agent and the level of at least one cytokine is compared with a threshold level. In one embodiment, the cytokine is FLT3-L, TNF-xcex1 or TGF-xcex2. In other aspects, the method involves using the threshold level to guide treatment, so that when the threshold is approached or crossed, treatment is halted or decreased until the threshold is no longer approached or crossed.